Small Cells are low power, low-cost base stations that are able to provide cellular service in residential or enterprise environments, with a typical coverage range of tens of metres. They have auto-configuration and self-optimization capabilities that enable a simple plug and play deployment, and are designed to automatically integrate themselves into an existing macrocellular network. Small cells, often referred to as pico cell, or metro cell, typically use the customer's broadband internet connection, for example DSL, cable or the like, as backhaul towards the macrocellular network. Support of non-ideal backhaul (with one way latency of few milliseconds to few tens of milliseconds) between small cells and between small cell and macro cells is considered as the typical deployment scenario.
Small cell deployment for handling the capacity needs in high traffic areas, such as hot spot areas, is an area of current investigation. One proposal for handling the capacity needs in high traffic areas is to provide dual connectivity support for user equipment. Dual connectivity support allows a User Equipment (UE) to be connected concurrently connected to a macro cell and a small cell, or indeed to two small cells. In other words, the UE can be connected to more than one cell at a time and the UE can be served by more than one cell at a time. Dual connectivity support is considered as a way to enable offloading of traffic when required.
However, dual connectivity support raises a number of issues relating to Radio Resource Control (RRC) plane architecture.
It is desirable to provide a RRC architecture which simplifies UE implementation/operation as well as avoiding the need for inter-protocol communication over an open interface.